Thermodynamics of Gas–Liquid Criticality: Rigidity Symmetry on Gibbs Density Surface

摘要: The thermodynamic state function rigidity, defined simply as $$(\mathrm{d}p/\mathrm{d}\rho )_{T}$$ , where p is the pressure, $$\rho $$ density and T temperature, work required to reversibly increase of a fluid. Along any isotherm, rigidity $$(\omega )$$ decreases with for gas phase increases liquid. Thermodynamics, therefore, can define distinction between For one-phase system, everywhere positive, in two-phase region $$\omega =0$$ . temperatures above critical coexistence, has constant value mesophase that separates percolation loci, which bound limits existence liquid phases supercritical region. law rectilinear diameters extends defining line colloid-like inversion gas-in-liquid liquid-in-gas. Every equilibrium corresponding isothermal on same rigidity. We illustrate this symmetry empirically using literature (p,T)$$ equations-of-state some real fluids, notably carbon dioxide, water steam, argon. At molecular level, be explained by correspondence statistical properties available holes sites clusters equivalent number fluctuations complementary states